Ab initio quantum-mechanical and experimental mechanistic studies of Diels-Alder reactions between unsubstituted and phenyl-substituted acetylenes and 1,2,4,5-tetrazines

Article abstract of DOI:10.1021/ja00057a019

1,2,4,5-tetrazine (2a) undergoes thermal addition to phenylacetylene (1b) in dioxane with ΔH^? = 15.8 kcal/mol and ΔS^? = -31 cal/(mol·K). The activation parameters for the corresponding addition of 1b to 3-phenyl-1,2,4,5-tetrazine (2b